Multichannel cyclophon



Patented July 5, 1949 MULTICHANNEL CYCLOPHON Mauricef Arditi, New York, and Irwin Harold Franzel and Joseph Feinstein, Brooklyn, N. Y., assignors to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application March 22, 1947, Serial No. 736,434

October 5, 1946, there is described a demodulator using a single cathode ray tube which is also used to select one of a plurality of channels of time displaced pulses. Where a plurality of channels are to be selected, it becomes necessary, in said sysstem, to utilize a plurality of cathode ray tubes.

In the system of said application, time--displaced pulses are translated into pulses of variable width by providing voltages for cyclically deecting a beam over a secondary emitting target element and having the beam turned on by the incoming pulses. Depending on the time displacement of the incoming pulses, the beam initially strikes vdiiierent portions of the target element. Thereafter, as the beam is swept over the rest of the target elementit is maintained turned on by means of a feed-back voltage developed between the target element and the collector element until the beam is swept oi the target element whereupon the feed-back ceases and the beam is turned off. The variable width output pulses thus produced may be integrated to produce amplitude-modulated energy.

An object of the present invention is the pro- 4 Claims. (Cl. 177-353) vision of an improved demodulator and distributor system for multi-channel time displaced pulses in which a single cathode ray tube is used to distribute and demodulate the pulses belonging to a number of channels.

Another object is the provision of a demodulation and distributor system of the type described in the foregoing paragraph in which use is made -of the translating arrangement hereinabove mentioned in connection with the copending application.

The above mentioned and other features and objects of this'invention will become more ap- .parent and the invention itself, though not neces- Fig. 3 is a set of curves used in explaining the operation of the system of Fig. 1.

The present yinvention is herein described in relation to a multiplex time displaced pulse communication system of the type having recurrent series of pulses such as for example, the series sho'wn in curve A, Fig. 3, each series including a plurality of signal pulses as for example, pulses I, 2, 3, etc. following a marker signal 4, which latter may consist for example, of a pair of pulses having a different spacing from each other than the signal pulses. The successive signal pulses of a series each form part of a different channel. Thus for example, pulses I, 2 and 3 are each part of a different channel. The signal pulses are time displaced with relation to their position following the marker signal, with pulse I being represented in its unmodulated position, and the vertical dotted lines on either side thereof indicating the limits of its modulation, while pulse 2 is represented at one extreme of modulation and pulse 3 at the other extreme. These pulses which may be transmitted via any suitable transmission medium, may be received on a receiver 5 in which they may, for example, be amplied and have their carrier frequency removed. The output pulses are fed over a line 6 through a. blocking condenser I and resistor 8 to the control elementor control grid 9 of an electron gun I0 in a cathode ray tube II. The gun I0 also includes a cathode I2. The system is arranged so that the output pulses from receiver 5 are used to turn on the beam. The beam I3 is deected by any suitable means, such as, for example, a pair of electrostatic deecting plates I4, to which sweep voltages I5 are applied from a sweep voltage wave l generator I6. To synchronize the deflection of the beam with the marker signal 4, amarker separator I1 may be also coupled to the output of the receiver 5 and serve to separate the marker signal. The output of marker separator I1 is then used to trigger or control the sweep generator I6 and thereby produce synchronization.

The grid 9 is preferably normally biased to cutoff as for example, by means of a source of D. C. potential I8 in series with a resistor I9 applied between the cathode `I2 and grid Si.v The pulses delivered across line 6 and applied to the grid 9 are, however, suicient to overcome this bias and cause the beam to be turned on.

As the beam is deected, it passes, providing the beam is turned on, through the apertures 20, in

22 which are mounted behind the apertures 29 to be struck by the beam as it is directed into the apertures. A separate target element is provided for each channel, each of the target elements being connected in series with the input of a separate utilization device 29 which may be for example. a loud-speaker, amplifier, etc. The aperture plate 2| is at a higher positive potential than the target elements 22, as represented 'in Fig. 1, in which the highest positive point of the source of D. C. potential 24 is connected to the aperture plate 2 I, with an intermediate positive point connected through a resistor 2B in series with the inputs of the various utilization devices 23 to the target elements 22. A

Each time the beam hits any of the target elements, producing a flow of secondary electrons between that target element and the aperture plate, current will ilow through resistor 25, producing a voltage drop thereacross with the potential of end 29 rising in a positive direction. End 29 is coupled by means of a line 21, and a blocking condenser 28, back to the grid 9 and this positive potential causes an increase of the current in the primary beam until a point of equilibrium is reached. 'I'he beam continues at this level even though the pulse, which initially turned on the beam. has ceased, until the beam is ilnally deflected oil' the target element when the current iiow across resistor 25, falls with extreme rapidity.

In order to regulate the maximum current in the beam. use may be made oi means such as for example, a diode 29, in series with an adjustable source of bucking potential 30, which elements are arranged in parallel between the grid 9 and the cathode I2, being likewise parallel with the line consisting of resistor I 9 and source `of potential I9. By varying the amount of the value of the bucking voltage 30, the potential drop between resistor and cathode may be limited to the maximum level desired, and thereby limit the maximum beam current.

The system operates as a distributor, inasmuch l as the pulses belonging to thefdiierent channels are applied to diil'erent target elements which have separate utilization devices, each forming part of a separate channel. 'I'he system operates as a demodulator in a manner that may be readily understood in connection with the following description referring to Fig. 2. The beam is turned on by the incoming signal pulse applied to grid 9. Depending on the time of arrival of the pulse, that is its time displacement, the time when the beam is turned on will vary. Thus the beam will initially strike the target element at any one of a number of points. 'I'he beam Will continue to remain on until it has been deilected all the way across the aperture from the initial point of impingement to the end of the aperture. This would require a given length of time and the output pulse applied to the utilization device 23 would have a width or duration equal to said time. For example, designating the interval required to move the beam from its position at 3i, Fig. 2, to the end of the aperture as T1, and assuming that it is pulse 2 which causes the beam to flash on in the position 3l. the output pulse obtained will have a duration or width determined by the time required to move" the vbeam from its ,position at 2| until it has passed out of the aperture 2li.- Pulse 2 is at one extreme of time displacement. Assuming on the other hand, that a pulse having another modulation. as for example, pulse I, which is in the center of its modulation limits. such a puise might turn the beam on in the position indicated in dotted lines at 92. Due to the feedback voltage to the grid. the beam will .remain on until it has passed the rest of the aperture and the duration oi the output voltage produced, will occupy a time Tn. Thus the corresponding output pulse fed to the utilization device 23, would have a width corresponding to T2. as indicated in curve B, Fig. 3.

From the foregoing it will be seen that the output pulses will vary in width according to the time displacement of the signal pulses. These output pulses may be integrated in any suitable integrating device which may form part of each of the utilization devices 2l.

While we have described above the principles of our invention in connection with speciilc apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of our invenion;

We claim:

1. A cathode ray tube system for translating and distributing multi-channel time displaced pulses comprising, a cathode ray tube having beam forming means, a plurality of target elements, means for deiiecting said beam over the. target elements successively, means responsive" to each of the incoming pulses for turning on 'the beam so that the beam strikes diii'erent posi* tions of the target element associated with its channel depending on the time displacement of the pulse turning on the beam, means responsive. to Athe impingement of the beam on a target element for maintaining the beam turned on until the beam has been deected past said target element, whereby pulses of variable width are produced at the output of the utilization devices, and a plurality of target elements each having their inputs coupled to the output of a separate one of the target elements.

2. A cathode ray tube system according to claim 1, further including means i'or coupling one end of the input of saidv utilization devices to a separate one of said target elements, and means for coupling the other ends of said inputs together and to the beam forming means to feed back voltages to said beam forming means to maintain it in operation while the beam is impinging upon the target.

3. A cathode ray tube system according to claim 1 wherein said target elements are secondary electron emitting electrodes, and further including a collector for collecting said secondary electrons.

4. A cathode ray tube system accordingto claim 1 wherein said target elements' are secondary electron emitting elements, and further including a single collector electrode for collecting the secondary electrons, a source of potential, means including a resistor coupling said target elements to one point on said source, means coupling a higher point oi.' potential of said source to said collector, and means for feeding the potentials developed across said resistor upon impingement of the beam on any one of the target elements, back to the beam forming means, 'to maintain the beam forming means in .operation until the beam moves away from a target element.

MAURICE ARDITI..

IRWIN' HAROLD FRANZEL. JOSEPH FEINSTEIN.

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2,256,336 Beatty Sept- 16, 1941 pages 90 and 91. 

